Wildfire burn scars can intensify and even trigger thunderstorms, here’s how?

Synopsis: As per a research study, wildlife burn scars due to wildfires can increase thunderstorms. It increases the risk both of flooding and of lightning in the region.

Introduction

Wildfires burn millions of acres of land every year. It leaves behind Wildfire burn scars on the land with little vegetation and a darker soil surface, which cannot absorb the water. It makes the land more susceptible to flooding and erosion. Even small rainfall is sufficient to trigger flooding and debris flow.

Furthermore, burn scars can also increase thunderstorms and the risk of lightning that could spark more fires in the surrounding region.

What are factors that contribute to thunderstorms in burn scars?

3 factors contribute to thunderstorms in the burn scars: 1) lack of vegetation, 2) reduced soil moisture, 3) lower surface albedo (the amount of light or radiation the surface is able to reflect back).

Note: charcoal has an albedo of about 0.04 and fresh snow is nearly the maximum of 1.

How the factors result in increasing thunderstorms?

When soil is burned, it becomes darker. The darker surface absorbs more energy from the sun. It results in higher temperatures in burn scars compared to surrounding regions.

Temperature differences result in low air pressure in the burn scars and high pressure in the surrounding regions, causing convection (rising hot air and humid air from surrounding areas rush to fill the space). It further results in the formation of cumulonimbus clouds and even thunderstorms.

Example: In Australia, in 2003, a flash flood occurred. Scientists found that albedo in the burn area had fallen from 0.2 to 0.08. Scientists further found that if the land hadn’t been burned, just over a tenth of an inch of rain would have fallen.

Studies also found that the potential of burn scars to trigger rain decreases with the regrowth of vegetation.

Source: This post is based on the article “Wildfire burn scars can intensify and even trigger thunderstorms” published in Down to Earth on 9th September 2021.